This invention relates to a light-emitting semiconductor device such as that known as a light-emitting diode in common parlance, and more specifically to such a device fabricated in one piece with an overvoltage protector.
A host of specialists in light-emitting diodes have focused their attention in recent years on nitride semiconductors. The devices built using these materials emit light in the wavelength range of from 365 to 550 nanometers. The nitride semiconductor light-emitting devices have, however, an inherent weakness in withstanding electrostatic breakdown, being susceptible to destruction when subjected to a voltage surge in excess of 100 volts. It might be contemplated to incorporate an overvoltage or surge protector such as a discrete diode or capacitor in one and the same package with the light-emitting device. This remedy is unsatisfactory in consideration of the bulk of the resulting device caused factory in consideration of the bulk of the resulting device caused by the added number of component parts.
More sophisticated solutions are found in Japanese Unexamined Patent Publication Nos. 10-200159 and 10-135519, both suggesting an integration of an overvoltage protector with a light-emitting device. The former teaches a parallel connection of light-emitting device and protector diode on a sapphire substrate. The latter proposes to mount a protector capacitor on top of the light-emitting device on a sapphire substrate, the protector capacitor being also in parallel connection with the light-emitting device.
The suggestions made by these unexamined patent applications are both still objectionable in that the overvoltage protector is positioned to obstruct the emission of light, lessening the effective surface areas of the devices for light emission. This shortcoming may be restated that the devices must be made larger for given output light intensity. As an additional disadvantage, these prior art devices are both unnecessarily complex in construction and difficult of manufacture as they require conductors for electrical connection of the light-emitting device and overvoltage protector.